ChibiOS Free Embedded RTOS

I must be missing something fundamental here, I've looked at all the documentation and tried to find examples to help me figure this out, nothing seems to be working.

PROBLEM 1:

If I change a port mode like this, it works as expected and I am able to verify with a scope that the port is pulled up:



If I then try to do this in a for loop, the pad does not change to pullup:



If I try to use the bus method, again, I cannot get the port to pullup:



PROBLEM 2:

I attempted to use palReadBus(GPIOF) but it halts operation of my code. I also notice the docs that this returns a uint8_t typedef. The port I am reading is 16-bit. Can I read this in on read? If not, how do I read both halves of this bus? Really surprised it is halting the code.

I switched to using palReadGroup, but again, given the 8-bit vs 16-bit, it's just not making sense how I use it. I basically want to read all 16 bits into a 16-bit uint16_t.

Thanks!

Should I be using something like this:



And then using this with the bus functions? Still not sure on the 16-bit data though.

That was it! Going to leave this here for others that might be confused as to what to use with the Bus options.

A bus is a set of contiguous lines on a port that can be handled as a whole (atomically if the HW allows it).

A bus of 16 bits is equivalent to a port.

Giovanni

So is the documentation just limited to showing one implementation? The return type for portReadBus() shows it returned a uint8_t, but in the case of the STM32F4, the implementation appears to be returning 16 bits.

The documentation returns a stub implementation that is what you see under /os/hal/templates.

Low level details must always be studied on the MCU Reference Manual and looking at examples.

Giovanni

Ahhh, okay. That makes sense.

I will say, the examples for bus and group reading seem to be pretty sparse. I did a grep on the entire release and didn't find any examples showing how to use these. I extracted the usage from studying the FSMC example here:

http://www.chibios.org/dokuwiki/doku.ph ... ternal_ram


But even that does not do read/write bus or group showing how the PAL functions should work. Is there somewhere I should have seen these more in use?

Yes, it is true that it is not the most commonly used feature, I think because most have not yet understood what is it for.

It is for I/O abstraction, imagine you want to write a 44780 LCD driver and wanting to make it portable. This would not normally be possible because the display could be attached to different lines on different boards/MCUs.

If the driver is written to use a generic 4 bits bus for data, a 1 bit bus for RW and another 1 bit bus for the E signals then the driver would be portable because the bus definitions would be out of the driver code (in the board code for example).

Giovanni

What have people been doing? Writing to the port directly?

Personally I really like what you've done, now that I understand it.

I must admit that it is not an idea of mine

It is a feature of the AUTOSAR DIO driver that I included in PAL.

Giovanni